straightforward thiol-mediated protein labelling with dtpa synthesis of a highly active 111in-annexin a5-dtpa tracer简单thiol-mediated蛋白质标签的二乙三胺五醋酸合成高活性111 in-annexin a5-dtpa示踪剂.pdf

Kratz et al. EJNMMI Research 2012, 2:17 /content/2/1/17 ORIGINAL RESEARCH Open Access Straightforward thiol-mediated protein labelling with DTPA: Synthesis of a highly active 111In-annexin A5-DTPA tracer 1 1 1 1 2 1 Harald Kratz , Akvile Haeckel , Roger Michel , Lena Schönzart , Uli Hanisch , Bernd Hamm and Eyk Schellenberger1* Abstract Background: Annexin A5 (anxA5) has been found useful for molecular imaging of apoptosis and other biological processes. Methods: Here, we report an optimised two-step synthesis of annexin A5-diethylene triamine pentaacetic acid (DTPA) (anxA5-DTPA) for positron emission tomography (PET) and single-photon emission computed tomography (SPECT) imaging with a single purification step. The use of a recombinant annexin A5 (cys-anxA5) with a single thiol group allowed regionally specific coupling, without affecting the binding domain of cys-anxA5. Results: The metal complexing capacity of anxA5- DTPA was investigated by labelling with 111In3+ and Eu3+. Binding of modified anxA5-DTPA to apoptotic cells was tested in competition experiments with a fluorescent anxA5 derivative (anxA5-FITC) using flow cytometry and compared with that of wildtype anxA5 or non-binding anxA5-DTPA (M1234-anxA5-DTPA). The binding affinity to apoptotic cells of the anxA5-DTPA conjugate does not differ from that of wildtype anxA5. Conclusions: This two-step synthesis of annexin A5-DTPA resulted in biologically active anxA5-DTPA, which can be labelled with radionuclides for use in SPECT and PET imaging. Keywords: Annexin A5, Apoptosis imaging, PET, SPECT, DTPA, Indium Background Modifications are necessary before annexin can be used Targeting of ext